What are the options to make requests to an Android/ios application?

Question

Mobile development

Good afternoon!
Now the application is being written, we want to understand in what ways to implement requests from the server to a certain group of our users?
A group of users can be located in certain coordinates, or entered the application 20 minutes ago, or moved and stopped for more than 5 minutes, there may be different filters.
The application must send a response to a server request to a specific group of users.
All this manipulation is not visible to the user, but he can, at the first start, give permission for this method of collecting information.
Thank you !

Answer 1

I see 2 options:
1) keep in the background a service that communicates with the server all the time.
2) respond to push notifications sent by the server.
But in both cases, all the metrics that will determine who to send messages to should be initially defined. For example, in the case of "being in certain coordinates", constantly send the device coordinates to the server, or when receiving a request from the server, check the coordinates, and in case of suitable - display an alert.